drivers: gpio: Add GPIO support for mimx8ml8_m7 (NXP i.MX8M Plus SoC)

The current MCUX IGPIO driver assumes that the target SoC supports
the DR_SET, DR_CLEAR, and DR_TOGGLE functionality, but some do not
(namely, the M7 core of the i.MX8M Plus SoC). Current releases of
the MCUXpresso SDK IGPIO driver contain utility functions to set,
clear, and toggle pins which include provisions to support SoCs
with and without DR_SET, DR_CLEAR, and DR_TOGGLE, and this change
switches to using these utility functions.

Additionally, this change enables GPIO support on the mimx8ml8_m7
target.

Signed-off-by: Chris Trowbridge <chris.trowbridge@lairdconnect.com>